Pittsburgh's Catholic community has been rocked by the allegationsiStock

A federal prosecutor in the US may file a racketeering lawsuit against a Roman Catholic diocese after a state grand jury found two bishops guilty of covering up the abuse of hundreds of children.

Reports suggest that more than 50 clergy abused hundreds of children over a 40-year period at the Altoona-Johnstown diocese – based in Pittsburgh, Pennsylvania – following the conviction of Reverend Joseph Maurizo.

According to Press Association, 71-year-old Somerset County priest Maurizo was last year convicted of molesting two street children during missionary trips to Honduras. He was sentenced to nearly 17 years in prison, fined $50,000 and forced to pay his victims $10,000 each.

US Attorney David Hickton said on 1 April that the ongoing investigation over whether diocesan officials engaged in a pattern of criminal activity that would fall under the Racketeer Influenced and Corrupt Organizations Act (RICO), normally used to prosecute organised crime.

Abusive priests — described as "wolves disguised as shepherds" — were shuffled among parishes, according to a scathing 147-page grand jury report earlier in March. One priest was sent to a school for boys after a parent complained about the sexual abuse of her son.

Hickton's comments came after a grand jury report released last month by state Attorney General Kathleen Kane stated that the actions of Bishops James Hogan–who died in 2005 – and Joseph Adamec – who retired in 2011 – showed that a mass cover-up was underway.

The grand jury found that Hogan had held influence over the police and prosecutors in the diocese and often reassigned priests accused of molesting children instead of removing them from their duties. Adamec threatened accusers with excommunication and generally worked harder to hide or settle abuse allegations than to discipline the priests accused, the grand jury found.

An attorney for Adamec denied wrongdoing and said 14 priests accused of molestation under Adamec's watch were given psychiatric screenings. Nine were suspended or removed, and the five who were returned to ministry did not reoffend, Adamec's attorney said.

Bishops Joseph Adamec and James Hogan of the Altoona-Johnstown Diocese were accused by the grand jury of covering up an astonishing level of child sexual abuse. Hogan led the diocese from 1966 to 1986, and died in 2005. His successor Adamec retired in 2011. He refused to testify before the grand jury.

The investigation was based on a trove of secret diocese documents discovered after a search warrant was issued, the Christian Science Monitor reported.

Among the papers found was a chilling "cheat sheet" list of payments for child sex abuse. "Above clothing, genital fondling," for example, netted victim payments starting at $10,000, while victims of forced oral sex were paid up to $50,000, and "sodomy, intercourse" victims were paid $50,000 to $175,000 according to the diocesan records.